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Thread: EXT4 In Linux 3.5 Gets CRC32 Meta-Data

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  1. #1
    Join Date
    Jan 2007

    Default EXT4 In Linux 3.5 Gets CRC32 Meta-Data

    Phoronix: EXT4 In Linux 3.5 Gets CRC32 Meta-Data

    The pull request for the EXT4 file-system in the Linux 3.5 kernel and there's one prominent new feature...

  2. #2
    Join Date
    Mar 2010


    On-disk change , what about compatibility?

  3. #3
    Join Date
    Jan 2009
    Vienna, Austria; Germany; hello world :)


    It's an on-disk change, but it's gated by a superblock "feature flag".
    So unless you actually activate the feature, you won't get it. If you
    do activate the feature, then you won't be able to switch between
    older and newer kernel versions --- at least not and be able to mount
    the file system read/write. (We have different feature flags that
    indicate whether or not the kernel is allowed to mount the file system
    read/write, read/only, or not at all, if it doesn't know about a bit
    in the COMPAT, COMPAT_RO, or INCOMPAT feature bitmak.)

    The e2fsprogs support for this feature is currently only in the
    (rewinding) proposed update branch, so it's not something that I
    recommend people use just yet.
    Even though it's been pretty well
    tested, there are probably still some bugs we still need to shake out.

    - Ted

  4. #4
    Join Date
    Apr 2009


    I was wondering about that too. It would be expected that the user would have to do something to get the new feature since it is not backwards compatible.

    I'd say this is one of the reasons why every once in a while one should do a full backup, reformat and copy everything back

  5. #5
    Join Date
    Jan 2007


    So looks like we'll have to reformat to use this feature (in the future!), or will there be some conversion tooling? I know i could change the flag with tune2fs, but the metadata would needed to be rewritten for the crc32 value field?

  6. #6
    Join Date
    Dec 2011

    Default Checksum

    What about CRC-64?

    What about using a secure hashing algorithm such as SHA-1 or Skein?

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